It is now clear that the widespread belief that human infants are innately afraid of heights is incorrect. Previous animal research by Held and Hein had demonstrated the necessary role of active movement and self-produced visual stimulation in the appearance of wariness of heights as manifested on the visual cliff. Our previous human infant studies have confirmed that for most infants there is a period of time following the onset of locomotion when the infant does not manifest intense fear of heights, followed by intense avoidance of heights. In the proposed studies, we intend to investigate the role of "artificial" self-produced locomotion provided by a locomotor aid to prelocomotor infants to confirm whether self--produced locomotion is playing an important role in the development of wariness of heights in human infants, as it does in animals. We are also investigating the impact of locomotor impediments created by the need to wear orthopedic appliances in the manifestation of fear of heights in young infants. Finally, we are studying the perceptual consequences of the development of self-produced locomotion for the development of space and form recognition.